/*******************************************************************************
* SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU Lesser General Public License Version 2.1 or later (the
* "LGPL"), in which case the provisions of the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of the LGPL, and not to allow others to use your version of
* this file under the terms of the EPL, indicate your decision by deleting
* the provisions above and replace them with the notice and other provisions
* required by the LGPL. If you do not delete the provisions above, a recipient
* may use your version of this file under the terms of the EPL or the LGPL.
* 
* Based on the original MiniSat specification from:
* 
* An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
* Sixth International Conference on Theory and Applications of Satisfiability
* Testing, LNCS 2919, pp 502-518, 2003.
*
* See www.minisat.se for the original solver in C++.
* 
*******************************************************************************/
package org.sat4j.minisat.learning;

import org.sat4j.minisat.core.Constr;
import org.sat4j.minisat.core.DataStructureFactory;
import org.sat4j.minisat.core.ILits;
import org.sat4j.minisat.core.IOrder;
import org.sat4j.minisat.core.Solver;

/**
 * Learn clauses with a great number of active variables.
 * 
 * @author leberre
 */
public class ActiveLearning<L extends ILits,D extends DataStructureFactory<L>> extends LimitedLearning<L,D> {

    private static final long serialVersionUID = 1L;

    private double percent;

    private IOrder<L> order;

    private int maxpercent;

    public ActiveLearning() {
        this(0.95);
    }

    public ActiveLearning(double d) {
        this.percent = d;
    }

    public void setOrder(IOrder<L> order) {
        this.order = order;
    }

    @Override
    public void setSolver(Solver<L,D> s) {
        super.setSolver(s);
        this.order = s.getOrder();
    }

    public void setActivityPercent(double d) {
        percent = d;
    }

    public double getActivityPercent() {
        return percent;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.sat4j.minisat.LimitedLearning#learningCondition(org.sat4j.minisat.Constr)
     */
    @Override
    protected boolean learningCondition(Constr clause) {
        int nbactivevars = 0;
        for (int i = 0; i < clause.size(); i++) {
            if (order.varActivity(clause.get(i)) > 1) {
                nbactivevars++;
            }
        }
        return nbactivevars > clause.size() * percent;
    }

    @Override
    public String toString() {
        return "Limit learning to clauses containing active literals ("+percent*100+"%)"; //$NON-NLS-1$
    }

    public void setLimit(int percent) {
        maxpercent = percent;
    }

    public int getLimit() {
        return maxpercent;
    }
}
